APPENDIX 30I (2) also by passing a mixture of hydrogen cyanide and hydrogen chloride into a phenol ether in presence of A1C13, /OCIL, C6IIBOCII3 + HCN.IIC1 - Q-M4< " + IIC1. XCII:NH The product is then hydrolysed with hydrochloric acid (Gattermann), /OCII3 /OCII, Q>n4< +iiŤo = c;Hii4<: XCII:NII " -CllO (3) Grignard's reaction can also be used for preparing aromatic aldehydes (p. 308). The numerous reactions which benzaldehyde undergoes are described in this preparation, and in some of the subsequent ones (see Preps. 93-97). On reduction, benzaldehyde yields, in addition to benzyl alcohol, a pinacone known as liydrobenzoin, c,,iiacoii cyr5cnoH + H3 - I QjIIgCOH CBII5CIIOII Hydrobenzoin. PREPARATION 89. a- and /3-Benzaldoximes.The existence of two isomeric benzaldoximes was first observed by Beckmann in 1889, vyho explained their relation by a difference 'in structure. C6H5CH:NOH C6H5CH.NH \/ O a-Benzaldoxime. jS-Benzaldoxime. In the following year Hantzsch and Werner published their theory, by which the greater number of isomeric oximes both of aldehydes and ketones have found a satisfactory explanation. These compounds were not structurally but stereo-isomeric, the relation being similar to that which exists between fumaric, maleic or mesaconic and citraconic acids (p. 265), or again between the two diazotates of potassium (p. 283), and which may be represented as follows : C6H5.C.H C8H8.C.H HO.N N.OH a-Benzaldoxime. jS-Benzaldoxime.